1. Field of the Invention
This invention relates to improvements in a method and apparatus for assisting in the discharge flow of material which has caking or sticking tendencies so as to set up and not flow freely by gravity in bins for flowable material.
2. Prior Art
When handling certain materials which are ordinarily free-flowing it is well known in the art that such materials sometimes tend to cake, compact, "set up", or otherwise become hard and non-flowable. Such conditions sometimes result in what is known as "ratholing" and "bridging" in silos. In conventional silos such problems result in various measures being taken to cause such materials to flow again. Such measures include placing vibrators on the hoppers of conventional hopper-type bins, simply pounding a hopper-type bin with a sledge hammer, or sending men inside the bin with picks, shovels and other manual implements to break up the caking material. This latter procedure is extremely dangerous. Men have been killed when bridges or rat holes have collapsed and the material in the bin falls. Additionally, bins have been destroyed by implosion when there is a collapse of caking material which bridges within the bin. The degree of caking depends upon the particular material involved.
There is previously known in the art, as shown for example by U.S. Pat. No. 4,421,250 granted Dec. 20, 1983, U.S. patent application Ser. No. 307,089 filed Sept. 30, 1981 and published European International Application No. WO82/03839, and as marketed commercially by All-Flow, Inc. of Buffalo, N.Y., a gravity discharge bin for relatively free-flowing granular material in which the gravity discharge is assisted by pneumatic pressure acting upon a liner to nudge the material into the top of an inverted cone formed at an angle of repose after the material has emptied itself by gravity.
While prior art bins are useful with materials which are completely free-flowing and partially free-flowing, they have a limitation in connection with materials which severely cake, compact or agglomerate, i.e., materials which would ordinarily flow, but when they take up moisture they become so compacted that they will not flow and hence will not discharge by gravity. In such a case any assist by vibration or push on the material in the bin by a liner will not assist the gravity discharge as there is no gravity discharge to start out with and the bin will not empty.